PLATE V. 



POTERIOCRINUS MAGNIVENTRUS, Sp. IIOV. 



Keokuk Group, Crawfordsville, Indiana. 



Fig. la. Posterior view of calyx, with base of arms and origin of ventral sac; showing the 

 longitudinar ribs resembling jointed arms, and transverse folds; part of IBB 

 broken off. Coll. Yale University Museum. 

 16. Anterior view of same, showing strongly plated integument passing into the ventral 

 sac; a Platyceras in commensal attachment, indicating that anal opening was 

 near base of sac, on anterior side. 



2. Part of \entral sac of very large specimen, considerable,- flattened and wider than 



in life; the Ijeak of a Platyceras may be seen at the lower end, showing that top 

 of calyx was a little below that level; some ends of arms are seen curving over 

 at the upper end. Same collection. 



3. Distal end of sac of another specimen; apex restored from impression in the matrix, 



showing how it tapers to a point. 



Graphiocrinus encrinoides de Koninck and Lehon. 



Lower Carboniferous. Tournai, Belgium. 



Fig. 4. A nearly complete crown, posterior view; with anal plate in place, resting upon 

 truncate post. B, and rising above level of IIR. X 2. 

 5. Posterior view of another specimen showing same structures; the anal plate is 

 apparently transversely flivided by a faint suture. X 2. 



